Screen printing machine with interchangeable cylinders



Dec. 13, 1966 J. B. VAN DER WINDEN 3,291,044

SCREEN PRINTING MACHINE WITH INTERCHANGEABLE CYLINDERS Filed Sept. 11, 1964 2 Sheets-Sheet 1 INVENTOR. JOHANNES B. VAN DER WINDEN LQME. a

ATTORNEYS.

Dec. 13, 1966 J. B. VAN DER WINDEN 3,291,044

SCREEN PRINTING MACHINE WITH INTERCHANGEABLE CYLINDERS Filed Sept. 11, 1964 2 Sheets-Sheet 2 JQHANNES B. VAN DER WINDEN ATTORNEYS.

United States Patent Ofiice 3,29Lfi44 Patented Dec. 13, 1966 3,291,044 SCREEN PRINTING MACHINE WITH INTERCHANGEABLE CYLINDERS Johannes Bernardus van der Winden, Amstelveen, Netherlands, assignor to Gebr. Stork & Cos Apparatenfabriek N.V., Amsterdam, Netherlands Filed Sept. 11, 1964, Ser. No. 395,880 Claims priority, application Netherlands, Sept. 12, 1963,

297,814 Claims. (Cl. 101118) My invention relates to a screen printing machine comprising an endless belt for supporting the material to be printed upon, which belt is adapted to move in a continuous path and travels between a driving pulley and an idler pulley along a substantially straight opea-rtive path, and further comprising a number of bearing devices for cylindrical screens, mounted along said path, which screens are adapted to cooperate with the supporting belt.

The supporting belt of course is not in itself rigid enough to resist the pressure exerted by the screens during operation. Hitherto a table top or a similar surface, over which the supporting belt travels, has been disposed underneath the belt. This involves some problems, the most important of which is the friction occurring between the belt and the table. This friction depends on the pressure which is exerted by the squeegee blade present in each of the screens. The frictional force causes an elongation in the supporting belt, which elongation affects the registration between the consecutive screens. This means that with a change of the pressure of the squeegee blade, and thus also of the frictional force exerted on the belt, a change in the elongation of the belt will occur, which necessitates an adjustment of the registration of one or more of the screens.

It is a first object of my invention to achieve in this respect a fundamental improvement, by providing means underneath the operative path of the supporting belt, for bearing and guiding the belt practically without friction so that a change of the squeegee blade pressure does not necessitate an adjustment of screen registration.

These bearing and guiding means preferably consist of a belt supporting roll located opposite each of the screens.

In the screen printing machines hitherto known, when the machine is started, each screen is lowered towards the supporting surface, and raised from it when the operation is interrupted. This movable arrangement naturally involves complications as regards the correct guidance of the screen during movement towards and from the supporting surface.

It is a further object of my invention to effect engagement and disengagement between the screen and supporting surface in an inverse manner by moving the surface relative to the screens and so that the pressure of the screens is absorbed by supporting rolls.

It is a still further object of my invention to provide means for obtaining a previously adjustable contact pressure of the screen against the material resting on the supporting belt and to be printed upon, in order to avoid the risk of an excessive force being exerted by the screen upon the belt.

It is important that it should be possible to use screens having different diameters in the screen printing machine according to the invention. This possibilty, however, involves two problems, viz. the path of the upward and downward movement, which must be adapted to the diameters of the screens, while furthermore the line of contact between the material to be printed upon and the screens should always be identical with a view to the quality of the printing.

My invention will be explained more fully by reference to the drawing, which illustrates an embodiment of the screen printing machine.

FIG. 1 shows a diagrammatic side view of the whole machine.

FIG. 2 shows the part of the machine to the left of FIG. 1 on an enlarged scale, the driving gear being visible.

FIG. 3 shows a portion of the part of the machine to the right of FIG. 1 on an enlarged scale, the displacing mechanism for the supporting rolls being visible.

As can be seen in FIG. 1, the screen printing machine consists of a frame 1, on which is arranged an endless belt 2, which is adapted to travel in a continuous path between a driving pulley 3 and an idler pulley 4. In the operative path 5 this belt 2 forms a surface for supporting the material 6 to be printed upon, which is unrolled from a supply roll, not shown. Mounted on the frame 1 is a driving motor 7, which transmits the driving force via a connecting rod 8 to the pulley 3. Above the path 5 are provided a number of bearing devices 9 for cylindrical screens 10. The material 6 printed upon is delivered, on the side of the machine to the left of FIG. 1, to an apparatus, not illustrated, for the further treatment of this material. On the underside of the continuous path traversed by the belt 2 is a device 11 for washing the belt, a tension device 12, and a device 13 for applying an adhesive layer on the belt 2, so that after passing around the idler 4 this belt can support the material 6 to be printed upon and grip it temporarily. After the material 6 has been released at the end of the machine to the left of FIG. 1, the remnants of adhesive are removed from the belt 2 by meansof the Washing device 11.

Along the operative path 5 of the supporting belt 2 a supporting roll 14, on which the belt 2 rests, is arranged opposite each of the screens 10. These supporting rolls 14 are adapted to move towards the corresponding screen 10 and away from it. This can best be seen in FIGS. 2 and 3.

For this purpose each supporting roll 14 is mounted on a lever 15, which is adapted to pivot about a fixed pivot 16. The levers 15 are jointly operated by a rod 17, which is mounted pivotally on an arm 13, which is rotat ably connected at 19 with the frame of the machine and is connected at its other end 24) with a piston rod 21 of a hydraulic adjusting piston 22. Furthermore there is a stop 23 adapted to pivot about a shaft 24. The cylinder 22 is able to move the arm 18 away from the stop 23, in which case the supporting rolls 14 are lowered and the belt 2 is released from the screen 10 (position shown in FIG. 2). The cylinder 22, however, can also move the arm 18 in the other direction, so that this arm comes into contact with the stop 23 (position shown in FIG. 3). Thus the belt 2 is lifted slightly by the supporting rolls 14 as compared with the free position according to FIG. 2, so that contact can be established between the material 6 resting on this belt and the screens Ill.

The screen printing machine according to my invention is suitable for the use of screens having two different dia-meters. These screens are designated diagrammatically in FIG. 3 by 10 and 10". With a view to this, the stop 23 is formed by a cam with two boundary profiles 25 and 25", in consequence of which two positions for each supporting roll 14 are demarcated. These positions are designated by I and II in FIG. 3. These positions are demarcated in such a Way that they are symmetrical relative to a plane parallel to the operative path of the supporting belt 2 and passing through the pivot 16 of the lever 15'. In this way it is ensured that the zone along which each of the screens 10 comes into contact with the material 6 to be printed upon is invariably situated vertically below the centre of each screen.

The curvature of the boundary profiles 25' and 25" is not concentric with the shaft 24 of the stop 23. I Thus it is possible, by means of a small pivoting movement of the stop, to obtain some correction or adaption of the operative position of the supporting rolls 14. For this purpose the stop 23 is provided with an arm 26, which not only makes possible an adjustment through 180 (when passing from the use of a small screen to that of a large screen 10 or vice versa), but by means of which it is also possible to effect a small adjustment for the abovementioned purpose.

In the screen printing machine according to my invention, in which the screens 10 are positively driven, it is now possible to bring the material to be printed upon into contact with the screens and to release them therefrom again by raising the supporting belt with the aid of the supporting rolls. The screens themselves with their driving gear can therefore be supported immovably and very accurately in the frame of the machine. Moreover, ready adjustment to the diameters of the screens is possible.

What I claim is:

1. A screen printing machine comprising an endless belt for supporting material to be printed upon and movable in a continuous path about and between a driving pulley and an idler pulley, said path including a substantially straight operative portion, a number of stationary bearing devices each rotatably supporting a cylindrical screen and mounted along said operative portion of the path, said screens being adapted to print upon material carried on the supporting belt, a supporting roll located opposite each of the screens and on the other side of the belt from the screens for bearing and guiding the belt, and means for shifting each said roll to diiferent fixed positions of its axis relative to the associated screen including means for adjustably varying said fixed positions to move the belt toward and away from the screen, whereby to adjust the friction of the belt and material with respect to said rolls and screens and to permit substitution of screens of different diameter in the stationary bearing devices.

2. A screen printing machine according to claim 1 wherein said means for adjustably varying the positions of the supporting rolls comprises adjustable stop means for limiting their movement toward the screens.

3. A screen printing machine according to claim 1 wherein each supporting roll is mounted on an arm pivot- 4 able about a fixed pivot, an adjustable stop being provided for demarcating two positions of the arms, said positions being symmetrical relative to a plane parallel to the operative portion of the path of the endless belt and passing through the pivot of the arms.

4. A screen printing machine according to claim 3 wherein each said arm is a bell-crank lever, one leg of each lever carrying the supporting roll, the other leg of each lever being connected to a common control rod for all of the levers, a fluid pressure cylinder device connected to said rod for moving the rod to bring all of the roll supporting levers int-o either of said two positions of the arm, said adjustable stop including a cam having a profile with at least two different active sections.

5. A screen printing machine comprising an endless belt for supporting material to be printed upon and travelling between a driving pulley and an idler pulley so as to form a straight operative path, a number of bearing devices each for a cylindrical screen lying along said path, means for bringing the screens into and out of contact with said endless belt and including a support roll disposed under the belt opposite each said cylinder for raising and lowering the belt, each supporting roll being mounted on a lever adapted to pivot about a fixed pivot, an adjustable stop being provided and formed by a cam with two boundary profiles which demarcate two positions of the lever for each supporting roll, said positions being symmetrical relative to a plane parallel to the operative path of the endless belt and passing through the pivot of the lever.

References Cited by the Examiner UNITED STATES PATENTS 1,764,261 6/1930 Heileman 10 1-116 1,791,157 2/1931 Brasseur 101118 2,220,242 11/ 1940 Hildebrandt 101'1l6 2,511,511 6/1950 Murphy 101-420 2,697,397 12/1954 Bailey 101- 119 ROBERT E. PULFREY, Primary Examiner.

H. P. EWELL, Assistant Examiner. 

1. A SCREEN PRINTING MACHINE COMPRISING AN ENDLESS BELT FOR SUPPORTING MATERIAL TO BE PRINTED UPON AND MOVABLE IN A CONTINUOUS PATH ABOUT AND BETWEEN A DRIVING PULLEY AND AN IDLER PULLEY, SAID PATH INCLUDING A SUBSTANTIALLY STRAIGHT OPERATIVE PORTION, A NUMBER OF STATIONARY BEARING DEVICES EACH ROTATABLY SUPPORTING A CYLINDRICAL SCREEN AND MOUNTED ALONG SAID OPERATIVE PORTION OF THE PATH, SAID SCREENS BEING ADAPTED TO PRINT UPON MATERIAL CARRIED ON THE SUPPORTING BELT, A SUPPORTING ROLL LOCATED OPPOSITE EACH OF THE SCREENS AND ON THE OTHER SIDE OF THE BELT FROM THE SCREENS FOR BEARING AND GUIDING THE BELT, AND MEANS FOR SHIFTING EACH SAID ROLL TO DIFFERENT FIXED POSITIONS OF ITS AXIS RELATIVE TO THE ASSOCIATED SCREEN INCLUDING MEANS FOR ADJUSTABLY VARYING SAID FIXED POSITIONS TO MOVE THE BELT TOWARD AND AWAY FROM THE SCREEN, WHEREBY TO ADJUST THE FRICTION OF THE BELT AND MATERIAL WITH RESPECT TO SAID ROLLS AND SCREENS AND TO PERMIT SUBSTITUTION OF SCREENS OF DIFFERENT DIAMETER IN THE STATIONARY BEARING DEVICES. 